Treatment Of Textile Dye Wastewater Research Articles

Comparative treatment of textile dye wastewater with chemical coagulants and bacterial exopolysaccharides

Traces of chemical coagulants, such as alum, commonly used in wastewater treatment, remain in the water effluent and also result in secondary sludge that is difficult to treat. On the other hand, Extracellular Polymeric Substances (EPS) are safer and can be used as alternative bio flocculants. A study was hence done to compare the effectiveness of the treatment of Reactive Black 5 (RB5) textile wastewater with chemical coagulants and bacterial EPS. The jar test method was used to treat the wastewater with Alum and Polyferrous Sulphate (PFS) at varied pH (2–10) and respective dose concentrations. EPS was produced by bacteria isolated from cotton gin trash soil collected from Kitui ginnery in Kenya. EPS treatment was done at 30 °C for 72 h. EPS-producing bacteria isolates were identified by molecular analysis. The chemically and EPS-treated wastewater was analyzed for color, Total Dissolved Solids (TDS), and Chemical Oxygen Demand (COD). Respective color and TDS removal capacity by PFS and alum were (86.1% and 42.18%) and (85.1% and 69%) at their optimal conditions of (pH 7 and 100 mg/L) and (pH 7 and 140 mg/L). Similarly, PFS and alum reduced COD by 27.25% and 26.65%. Respective dye removal by YEAK2 −5 and YEPD K2 −2 EPS was 69.1% and 85.7%. However, YEPD K2 −2 and YEAK2 −5 EPS caused a respective rise of TDS by 40.14% and 67.17%. The respective reduction of COD by YEPD K2 −2 and YEAK2 −5 EPS was 56.25% and 54.24%. The chemically and EPS-treated wastewater met the National Environment Management Authority (NEMA) limits. The YEPD K2 −2 and YEAK2 −5 isolates were both identified as Bacillus sp. GC–MS and FTIR analysis results indicated that the two EPS were heteropolysaccharides composed of different sugar derivatives and hydroxyl as the main functional group. The results for treatment of the dye wastewater by Alum, PFS, and EPS were therefore comparable. The bacterial EPS bio flocculants can therefore serve as effective and cleaner substitutes to the alum and PFS chemical coagulants.

Unleashing the potential of electrooxidation and PVDF/TiO2 photocatalysis for textile dye wastewater treatment

Unleashing the potential of electrooxidation and PVDF/TiO2 photocatalysis for textile dye wastewater treatment

Investigating the efficiency of electrocoagulation using similar/dissimilar electrodes for the detoxification of Coralene Rubine dye: a cost effective approach.

Efficient treatment of textile dyeing wastewater can be achieved through electrocoagulation (EC) with minimal sludge production; however, the selection of the appropriate electrode is essential in lowering overall costs. Also, the reuse of the treated aqueous azo dye solution from this process has not been explored in detail. With these objectives, this study aims to treat synthetic azo dye solutions and achieve high colour removal efficiency (CRE%) using similar (Ti-Ti) and dissimilar (Ti-Cu) metal electrodes through EC with an attempt to reduce the cost. The aqueous Coralene Rubine GFL azo dye was used to examine the efficiency and cost of the EC process. X-Ray Photoelectron Spectroscopy was used to study the EC mechanism, while High Performance Liquid Chromatography was used to analyse the degradation of the dye and the formation of intermediate compounds. The concentration of metal ions in the treated dye solution was quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), with Ti-Ti treated solution having 14.20mg/L concentration of Ti and Ti-Cu treated solution having 0.078mg/L of Ti and 0.001mg/L of Cu, respectively. Colour removal efficiency of 99.49% was obtained for both electrode sets, with a lower operating time and voltage for dissimilar metal combination. Ecotoxicity studies showed negligible toxicity of Ti-Cu treated dye samples compared to untreated solutions. Survival rate, protein estimation, and catalase activity was used to validate the treatment method's efficacy. The study found that the dissimilar electrode material exhibited reduced toxicity due to the presence of heavy metals below the permissible limit.

Comparative analysis of feed-forward neural network and second-order polynomial regression in textile wastewater treatment efficiency

<abstract><p>This study refines a single-layer Feed-Forward Neural Network (FFNN) for the treatment of textile dye wastewater, concentrating on percentage decolorization (%DEC) and percentage chemical oxygen demand (%COD) reduction. The optimized neural network configuration comprises four input and one output neuron, fine-tuned based on the mean squared error (MSE). The training phase demonstrates a consistent MSE decline, reaching its lowest at epoch 209 for %DEC and epoch 34 for %COD, with corresponding MSEs of $1.799 \times 10^{-5}$ and $ 1.4 \times 10^{-3} $, respectively. The maximum absolute errors for %DEC and %COD were found to be $ 4.0787 $ and $ 2.4486 $, while the mean absolute errors were $ 0.4821 $ and $ 0.7256 $, respectively. In contrast to second-degree polynomial regression, the FFNN model exhibits enhanced predictive accuracy, as indicated by higher $ R^2 $ values of $ 0.99363 $ for %DEC and $ 0.99716 $ for %COD, and reduced error metrics.</p></abstract>

A parametric study on intensified degradation of textile dye water using hydrodynamic cavitation based hybrid technique

In this paper, a detailed investigation of the treatment of model textile dye wastewater (MTDW) by applying a hybrid approach of hydrodynamic cavitation (HC) coupled with UV light and different oxidants is reported. A distinct hybrid strategy of HC combined with inline UV and different oxidants was employed to treat model textile dye wastewater comprising mixed dyes under neutral to alkaline conditions and in the presence of salt and detergent, which form significant components of textile wastewater. The model textile dye wastewater was made of three dyes: Reactive Yellow 84, Reactive Black 8, and Reactive Violet 5 with 100 ppm of total concentration. Effects of various operating conditions, such as feed pressure at the venturi inlet, initial pH, process time, and different oxidizing agents, on percentage COD reduction were investigated. The extent of dye decolourization using HC combined with different oxidizing agents, viz., hydrogen peroxide (H2O2), sodium persulfate (NaPS), and potassium peroxymonosulfate (PPMS), were studied. HC coupled with UV and potassium peroxymonosulfate (PPMS) oxidant produced maximum decolourization of dyes to the extent of 100 % at pH 7. A maximum COD reduction of 87.7 % was obtained at the optimized operation conditions of hydrodynamic cavitation (HC) coupled with UV and PPMS. The treatment of model dye wastewater utilizing a hybrid strategy of HC+UV+PPMS achieved a synergetic index of 1.92, which was significantly better than standalone treatments. The current work contributes significantly to our understanding of the performance of cavitation-based systems for treating complicated textile effluent.

Treatment of textile dye wastewater by peroxymonosulfate activation using facilely prepared Fe3O4@TiO2 heterogeneous photocatalyst

AbstractIn this study, Fe3O4@TiO2 was synthesized by a facile precipitation–impregnation method and applied as a magnetic photocatalyst for degrading synthetic and actual textile dyeing wastewater in the presence of peroxymonosulfate (PMS). In Rhodamine B (RhB) degradation, the removal efficiency reached 99.86% (for RhB) and 93.67% (for color) under optimal operating conditions of 80 mg L–1 RhB, 0.5 g L–1 PMS, 0.5 g L–1 Fe3O4@TiO2, at pH 6, and after 30 min of UVA irradiation. The influence levels of anions on the RhB removal and decolorization were in the order of Cl− < SO42− < CO32− < PO43−. In addition, the Fe3O4@TiO2 composite exhibited good applicability for treating other dyes (e.g., 99.6% of tartrazine and 60.3% of methylene blue after 30 min) in water and actual textile dyeing wastewater with high color (70.3% after 5 min) and COD removal (71.4% after 120 min). The radical scavenging tests indicated the role of reactive oxygen species in the order of O2•− ∼ 1O2 > h+ > SO4•− > HO• for RhB degradation but O2•− > h+ > 1O2 > SO4•− > HO• for decolorization. These results suggest the potential application of PMS activation using Fe3O4@TiO2 in the photocatalytic treatment of textile and dyeing wastewater with the dominant role of O2•−.

Comparison of aerobic and anoxic-oxic sequential batch reactors for treating textile wastewater

ABSTRACT The discharge of untreated textile dyeing wastewater containing azo dyes has significant ecological consequences. The incomplete biodegradation of these dyes can produce harmful and carcinogenic aromatic amines (AAs), which pose a threat to the environment. This study evaluates the treatment of real textile dyeing wastewater containing azo dyes by two different systems: an anoxic sequential batch reactor (A/O-SBR) and an aerobic sequential batch reactor (A-SBR). The effects of hydraulic retention time (HRT) on both systems were investigated in terms of chemical oxygen demand (COD), total nitrogen (TN), color, and AAs removal. Ranging between 85% and 92%, the COD removal efficiency was almost similar in the A/O-SBR and A-SBR systems, suggesting that the aerobic phase is primarily responsible for COD removal. However, A/O-SBR showed higher removal of color (90%) than A-SBR (75%) due to the presence of an anoxic phase. HRT has a significant impact on color removal in both systems. However, there was no significant effect on COD removal when HRT exceeded 12 h. According to LC-MS/MS analysis, increasing the HRT from 12 h to 24 h increased the AAs concentration in the anoxic phase, from 253 ng/L to 261 ng/L and slightly decreased the AAs concentration in the aerobic phase from 107 ng/L to 102 ng/L. This resulted in an overall improvement in both dye and AAs removal. The presence of aerobic phase in A/O-SBR and A-SBR demonstrates strong AAs removal capacity. GC-MS/MS analysis indicated that as the HRT of A/O-SBR and A-SBR increased, the number of by-products increased.

Heterogeneous Fenton treatment of actual textile and dyeing wastewater by α-Cu-FeOOH nanomaterial

This work reports the successful synthesis and application of α-Cu-FeOOH in heterogeneous Fenton treatment of actual textile dyeing wastewater. The material characteristics were analyzed by SEM, EDX, BET, FTIR, and XRD methods. In heterogeneous Fenton tests, the highest TOC and color removal efficiencies were found to be 46.88 and 37.98%, respectively, in the suitable conditions of Cu/Fe molar ratio = 5%, [H2O2] = 0.1 M, [α-Cu-FeOOH] = 0.6 g/L, pH = 7, and after 60 min. The values of color and TOC after treatment well met the discharge standard for textile dyeing wastewater (QCVN 13:2015/BTNMT, Column B). The presence of copper in the material enhanced the activation of H2O2 in heterogeneous Fenton reactions under neutral environments. Therefore, α-Cu-FeOOH material has great potential for practical application in textile wastewater treatment with an initial color of 185.6 mg/L and TOC concentration of 72.54 mg/L.

Occurrences and fates of per- and polyfluoralkyl substances in textile dyeing wastewater along full-scale treatment processes

Industrial wastewater is a substantial source of per- and polyfluoroalkyl substances (PFASs) in the environment. However, very limited information is available on the occurrences and fates of PFASs along industrial wastewater treatment processes, particularly for the textile dyeing industry where PFASs occur extensively. Herein, the occurrences and fates of 27 legacy and emerging PFASs were investigated along the processes of three full-scale textile dyeing wastewater treatment plants (WWTPs) based on UHPLC−MS/MS in combination with self-developed solid extraction protocol featuring selective enrichment for ultrasensitive analysis. The total PFASs ranged at 630-4268 ng L−1 in influents, 436-755 ng L−1 in effluents, and 91.5-1182 μg kg−1 in the resultant sludge. PFAS species distribution varied among WWTPs, with one WWTP dominated by legacy perfluorocarboxylic acids while the other two dominated by emerging PFASs. Perfluorooctane sulfonate (PFOS) was trivial in the effluents from all the three WWTPs, indicating its diminished use in textile industry. Various emerging PFASs were detected at different abundances, demonstrating their use as alternatives to legacy PFASs. Most conventional processes of the WWTPs were inefficient in removing PFASs, especially for the legacy PFASs. The microbial processes could remove the emerging PFASs to different extents, whereas commonly elevated the concentrations of legacy PFASs. Over 90% of most PFASs could be removed by reverse osmosis (RO) and was enriched into the RO concentrate accordingly. The total oxidizable precursors (TOP) assay revealed that the total concentration of PFASs was increased by 2.3-4.1 times after oxidation, accompanied by formation of terminal perfluoroalkyl acids (PFAAs) and degradation of emerging alternatives to various extents. This study is believed to shed new light on the monitoring and management of PFASs in industries.

DISCUSSION ON TREATMENT EFFICIENCY OF REACTIVE YELLOW 145 COLOR AND REACTIVE RED COLOR 194 BY GUM EXTRACTED FROM MORINGA OLEIFERA SEEDS

The treatment of wastewater , in general , and wastewater containing dyes , in particular, has long been studied, to find not only effective treatment methods but also treatment materials that do not generate additional pollutants. These should be eco- friendly and inexpensive material s which also , make use of discarded or rarely used resources. The current trend is towards a circular economy where waste from one industry is an input for another and helps to reduce environmental pollution. In this study, a biological coagulant (gum) extracted from moringa seeds is produced as a coagulant to treat Reactive Y e llow 145 (RY145) and Reactive Red 194 (RR194). The material's properties are determined by scanning electron microscopy (SEM) and FTIR analysis methods. SEM images show that the surface structure of the gum biomaterial extracted from moringa seeds has the appearance of relatively fine pores and relatively homogenously distributed gum particles on the surface. FTIR spectra indicate that the prepared material contains surface functional groups such as –OH, –HC=O , and C-O of the xyloglucan ring. The factors affecting the coagulation process of RY145 and R R 194 colors include pH, gum concentration, initial color, stirring speed , and stirring time. From the empirical results, it is suggested that the bio-flocculating agent (gum) prepared from moringa seeds, an eco-friendly material , can decolorize and reduce COD, and thus, possess great potential for application in the treatment of textile dyeing wastewater, with RY145 and COD removal efficiency of 87.77% and 76.92% respectively, and RR194 and COD removal efficiency of 89.31% and 80% respectively.

Treatment of textile dyeing wastewater using a low-cost adsorbent

A cost-effective adsorbent was synthesized from Eichhornia Crassipes using phosphoric acid as an activating agent and it was applied for the decolourization of the Textile dyeing industry’s effluent (TDE). Physical, chemical and morphologic characteristics were investigated using characterization studies, BET and XRD techniques. Batch experiments were performed to determine the optimum dosage, temperature, time and pH. The ideal conditions for treating TDE were found to be 30 °C, 1 g/L dose, 90 min, and pH 7. Maximum decolourization of 92%, reduction of COD and BOD were found to be 66.77% and 83.94% respectively with 50 T TDE. As a result, the aquatic weed Eichhornia crassipes can be employed as an efficient adsorbent to remove dye from wastewater.

The synthesization of activated carbon from electrocoagulated palm oil mill effluent sludge for wastewater treatment

The oil palm industry in Malaysia is certainly the one of economic and agricultural drives for the country. Nevertheless, despite the obvious benefits that it possesses, oil palm mill also significantly contributes to environmental degradation. It generates massive amounts of solid waste, wastewater, and air pollution from its production and processing processes. Activated carbon (AC) as an adsorbent has been used widely to remove pollutants in wastewater. Many attempts have been made to produce economically accessible AC. This paper explores the idea of producing an AC, a value-added product, sludge produced from the electrocoagulation process of palm oil mill effluents (POME) through chemical activation. AC has different applications after its discovery as a solid and reliable adsorbent. Its microporous structure, high surface reactivity, and surface area make it versatile and viable for removing pollutants from aqueous solutions. The electrocoagulated sludge-based AC is characterized by its surface characteristics, elemental compositions, surface morphology, and available functional group. To validate the adsorption capacity of electrocoagulated sludge-based AC, textile dye wastewater treatment was carried out to test the efficiency of AC. Results indicate that TSS in textile dye wastewater decreased as the adsorbent dosage increased. The values of TSS removal by AC from H3PO4 activation decreased steadily compared to KOH activation. Meanwhile, the color removal percentage decreased when the dye concentration increased. AC from H3PO4 activation has higher color removal percentage. This shows that AC from H3PO4 activation has better adsorption due to its more extensive surface area. From BET analysis, AC by H3PO4 activation offers a higher surface area, 36.1017 m2/g, compared than KOH activation, 8.9460 m2/g. Extensive surface area has a higher tendency to adsorb contaminations. The findings of this work confirmed the potential use of electrocoagulated sludge-based AC as an alternative and economically adsorbent for effective dye pollution removal in wastewater.

Plant-microbe-dye interaction during rhizoremediation

The conventional technologies used for textile dye wastewater treatment are costly, and involve high energy consumption and sludge production. However, bioremediation using plants and microbes involves low cost, energy consumption, and no sludge formation. Hence, the review focuses on the dye degradation by the plant-microbe treatment system.

Low-pressure thin-film composite nanofiltration membranes with enhanced selectivity and antifouling property for effective dye/salt separation

For better sustainable resource recovery and elevating the separation efficiency of dye/salt mixture, it is essential to develop an appropriate nanofiltration membrane for the treatment of textile dyeing wastewater containing relatively smaller molecule dyes. In this work, a novel composite polyamide-polyester nanofiltration membrane was fabricated by tailoring amino functionalized quantum dots (NGQDs) and β-cyclodextrin (CD). An in-situ interfacial polymerization occurred between the synthesized NGQDs-CD and trimesoyl chloride (TMC) on the modified multi-carbon nanotubes (MWCNTs) substrate. The incorporation of NGQDs significantly elevated the rejection (increased by ∼ 45.08%) of the resultant membrane for small molecular dye (Methyl orange, MO) compared to the pristine CD membrane at low pressure (1.5 bar). The newly developed NGQDs-CD-MWCNTs membrane exhibited enhanced water permeability without compromising the dye rejection compared to the pure NGQDs membrane. The improved performance of the membrane was primarily attributed to the synergistic effect of functionalized NGQDs and the special hollow-bowl structure of CD. The optimal NGQDs-CD-MWCNTs-5 membrane expressed pure water permeability of 12.35 L m-2h−1 bar−1 at the pressure of 1.5 bar. Noteworthily, the NGQDs-CD-MWCNTs-5 membrane not only showed high rejection for the larger molecular dye of Congo Red (CR, 99.50%) but also for the smaller molecular dye of MO (96.01%) and Brilliant Green (BG, 95.60%) with the permeability of 8.81, 11.40, and 6.37 L m-2h−1 bar−1, respectively at low pressure (1.5 bar). The rejection of inorganic salts by the NGQDs-CD-MWCNTs-5 membrane was 17.20% for sodium chloride (NaCl), 14.30% for magnesium chloride (MgCl2), 24.63% for magnesium sulfate (MgSO4), and 54.58% for sodium sulfate (Na2SO4), respectively. The great rejection of dyes remained in the dye/salt binary mixed system (higher than 99% for BG and CR, <21% for NaCl). Importantly, the NGQDs-CD-MWCNTs-5 membrane exhibited favorable antifouling performance and potential good operation stability performance. Consequently, the fabricated NGQDs-CD-MWCNTs-5 membrane suggested a prospective application for the reuse of salts and water in textile wastewater treatment owing to the effective selective separation performance.

Development of membrane bioreactor integrated ozonation using polyvinylidene difluoride composites for textile dyeing wastewater treatment

Development of membrane bioreactor integrated ozonation using polyvinylidene difluoride composites for textile dyeing wastewater treatment

Sustainable reuse of nickel converter slag as a heterogeneous electro-fenton catalyst for treating textile dyeing wastewater: Activity, mechanism and stability assessment

The high production and improper disposal of nickel converter slag (NCS) are raising serious concerns about its environmental impact, owing to the waste of resources and the foregone contribution to air, soil and groundwater pollution. This work uncovered that NCS could be reused as a superior catalyst for the treatment of textile dyeing wastewater by the heterogeneous electro-Fenton (hetero-EF) process. The NCS-laterite porous ceramsite (NLPC) catalyst showed the highest activity when the ratio of NCS to laterite was 3:2 and calcined at 900 °C. The methylene blue (MB) removal rate and chemical oxygen demand (COD) removal rate were 98.64% and 87.84%, respectively, after 30 min reaction under optimal operating parameters (100 g L−1 NLPC, 4 V of cell voltage and initial pH 3.0). Compared with the electro-Fenton (EF) system without NLPC catalyst, the degradation rate constant was increased by 223.9% (0.0452–1.464 min−1) and the energy consumption was reduced by 65.84% (2.02–0.69 kWh m−3). After six cycles, the MB removal rate only decreased by 5.35%, and the NLPC mass loss rate was 2.04%. Synergies between Co, Ni, Fe and Cu species to promote reactive oxygen species (ROS) generation were the predominant catalytic mechanism. Two possible pathways of MB degradation were deduced. In addition, the NLPC catalyst also showed excellent effects in different wastewater treatments. This work demonstrated an upgrade strategy for cleaner production of non-ferrous metallurgical by-products.

Kinetic Study for Startup of Aerobic Moving Bed Biofilm Reactor in Treatment of Textile Dye Wastewater.

Due to high augmentation in population and low availability of land, the quantum of wastewater production has surged resulting in advancements in wastewater treatment systems. To cope under such stressful circumstances, moving bed biofilm reactor (MBBR) proves to be an upgraded treatment technology for industrial and municipal wastewater treatment. The present startup study has been carried out using a laboratory-scale aerobic MBBR with working volume of 25L for textile dye wastewater treatment having AnoxKaldnes K3 media at filling percentage of 50%. In order to acclimatize the microorganisms on textile dye wastewater, the startup of the reactor was carried out using lactose as readily degradable co-substrate with textile dye wastewater in different ratios at hydraulic retention time (HRT) of 24h. The biofilm on the media was developed in 63days duration and the reactor attained pseudo-steady state (PSS) in 185days period. During PSS condition of the MBBR, the maximum chemical oxygen demand (COD) removal efficiency of 92% with mixed liquor suspended solids (MLSS) concentration of 4224 ± 22mg/L has been achieved. The kinetic study for biodegradation of textile dye wastewater has also been carried out using the Monodgrowth kinetics. The values of bio-kinetic coefficients of yieldof heterotrophic biomass (Y) and endogenousdecay coefficient for heterotrophic biomass (Kd) recorded are 0.394 mgVSS/mgCOD.d and 0.087day-1, respectively. The values of specific substrate removal rate (k), Monodhalf saturation constant (Ks), and maximumspecific growth rate for heterotrophic biomass (µmax) are 0.024 mgCOD/mgVSS.d, 53.203mg/L, and 0.0095day-1, respectively, demonstrating the suitability and healthy performance of MBBR for textile dye wastewater treatment.

Textile dyeing wastewater treatment by Penicillium chrysogenum: Design of a sustainable process.

In this work a parametric study and a bench bioreactor degradation test of Direct Black 22 (DB22) by Penicillium chrysogenum was performed as a first approach to an industrial application, framed within a policy of sustainable processes development. Three ancillary carbon sources and their optimum initial concentrations were studied. These were: glucose, potato starch and potato industry wastewater. Their optimum initial concentration was 6 g/L. The use of potato starch as co-substrate showed the highest decolorization rate and COD removal. Degradation of DB22 using different immobilization supports (stainless steel sponge, loofah sponge and polyethylene strips) was studied and the results showed that the time needed for the treatment decreased from 6 to 4 d. Phytotoxicity was evaluated in the final products of the immobilized cells assays, using Lactuca sativa seeds. For all treatments phytoxicity was reduced with respect to the untreated wastewater, except for the assays using polyethylene strips. Finally, the reuse of the biomass attached to different carriers and the performance of the treatment of DB22 in a 1 L bench scale bioreactor were tested. P. chrysogenum decolorized at least four sucesives reuses. The reactor assays showed a better performance of the treatment.

Intensification of ozone mass transfer for wastewater treatment using a rotating bar reactor

As one of the advanced oxidation processes (AOPs), ozonation has been widely used in the treatment of textile dyeing wastewater. However, ozonation was limited by the mass transfer process due to the low solubility of ozone in water. In this work, a novel rotating bar reactor (RBR) was developed to enhance ozone-water mass transfer via optimizing its inner structures. The RBR with the internal structure of sieve plates combined with spoiler columns has the best mass transfer performance, which was 249% higher than that of the RBR without these structures. Furthermore, the optimized RBR was adopted to intensify the decolorization of the simulated wastewater of reactive black 5. The ozone dose was used to characterize the introduced ozone mass for treating a liter of wastewater in different reactors. The ozone dose in RBR was 150 mg/L (using O3), which was lower than that in semibatch glass reactor (567 mg/L, using O3/UV/H2O2) and in cylindrical glass cell (506.67 mg/L, using O3/US), reported in the literatures. The results indicated that RBR can achieve the same decolorization rate with less ozone dose, i.e. the RBR is more efficient. The RBR exhibited great potential application in enhancing liquid-film controlling system.

Study on the Flocculation Performance of a Cationic Starch‐Based Flocculant on Humic Substances in Textile Dyeing Wastewater

AbstractDissolved organic matter is one of the difficult problems in the treatment of textile dyeing wastewater, among which humic substances are the most harmful to the environment and human health. Herein, cationic starch‐based flocculants are prepared by free radical polymerization of corn starch (St) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) in a redox‐initiated system of ammonium persulfate and sodium bisulfite. Corn starch‐graft‐poly(methacryloyloxyethyl trimethyl ammonium chloride) is denoted as St‐g‐PDMC. The St‐g‐PDMC is comprehensively characterized in terms of structural (element analysis, Fourier transform infrared, X‐ray diffraction, proton nuclear magnetic resonance spectroscopy), morphological (scanning electron microscopy), and thermal (differential scanning calorimetry) properties. Humic acid (HA) solution is selected to simulate negatively charged dissolved organic matter. The flocculation performance and mechanism of St‐g‐PDMC, cationic polyacrylamide (CPAM), and polymerized aluminum chloride (PAC) are systematically investigated. The experimental results show that St‐g‐PDMC functions mainly through the electric neutralization and bridging effect as the flocculation mechanism, CPAM using its own structure and the colloid formed by PAC through hydrolysis is more in line with the bonded bridging and net roll sweep trapping. The combined formulation of St‐g‐PDMC and PAC shows advantages over a single flocculant in the treatment of textile dyeing wastewater, and its cost is evaluated.